Reference is made to applicant's prior U.S. Pat. No. 4,360,051 that discloses and covers pneumatic and tire body ply carcass designs having both directional and non-directional construction and/or operating characteristics. Said prior patent also particularly refers to confluent body plies in pneumatic tire designs and wherein the term confluent plies is used to identify a tire body ply comprising two narrow body ply pieces of suitable cord fabric positioned within the tire carcass body so that the individual cords of one ply piece traverses the tire carcass from one bead to extend across the tire centerline at one commercially uniform bias angle and the individual cords of the second ply piece traverse the tire carcass a similar distance from the opposite bead which cords are angularly positioned at a like but opposite bias angle to the first cords to form a V-pattern where the individual cords meet and may overlap and extend beyond the tire centerline more than a marginal distance. These body and sidewall ply cords are at low rigidity bias angle ranges (2.degree. to 29.degree. to a radial line of the tire at the tire centerline) when compared to higher rigidity bias angles used in belt ply designs and may extend to the opposite tread shoulder area.
Specifically, the present invention relates only to circumferential (or directional) strength imbalance in belt ply cord designs positioned in the tire crown area wherein the two relatively narrow confluent ply pieces are not secured to a tire bead; they lie underneath respective tread shoulder areas of the tire and overlap the carcass centerline but do not extend to the opposite tread shoulder area, and wherein at least two confluent ply pieces overlap the circumferential centerline of the tire carcass significantly more than a marginal distance.
The confluent ply pieces are of known belt cord materials and positioned at high rigidity bias angles but unlike non-directional prior art ply belt design patterns because the confluent belt plies that rotate in a forward wheel direction possess greater cord reinforcement strength than the confluent belt plies that rotate in reverse wheel rotation. Therefore, the invention provides and teaches structural belt ply design to imbalance the circunmferential reinforcement strength of belt ply cord material with respect to direction of tire rotation, i.e. forward to reverse vehicle travel.